﻿#region Copyright 2010-2012 by Roger Knapp, Licensed under the Apache License, Version 2.0
/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#endregion
using System;
using System.Threading;

namespace CSharpTest.Net.Synchronization
{
	/// <summary>
    /// wraps the System.Threading.ReaderWriterLock lock, does not support read->write upgrades
	/// </summary>
	public class ReaderWriterLocking : ILockStrategy
	{
		private readonly ReaderWriterLock _lock;
		/// <summary>
		/// wraps the reader/writer lock
		/// </summary>
		public ReaderWriterLocking() : this(new ReaderWriterLock())
		{ }
		/// <summary>
		/// wraps the reader/writer lock
		/// </summary>
        public ReaderWriterLocking(ReaderWriterLock lck)
		{ _lock = lck; }

        void IDisposable.Dispose() { }

        /// <summary> Changes every time a write lock is aquired.  If WriteVersion == 0, no write locks have been issued. </summary>
        public int WriteVersion { get { return _lock.WriterSeqNum; } }

	    /// <summary>
        /// Returns true if the lock was successfully obtained within the timeout specified
        /// </summary>
        [System.Diagnostics.DebuggerNonUserCode]
        public bool TryRead(int timeout)
        {
            try 
            {
                _lock.AcquireReaderLock(timeout);
                return true;
            }
            catch (ApplicationException)
            { return false; }
        }

        /// <summary>
        /// Releases a read lock
        /// </summary>
        public void ReleaseRead()
        {
            _lock.ReleaseReaderLock();
        }

        /// <summary>
        /// Returns true if the lock was successfully obtained within the timeout specified
        /// </summary>
        [System.Diagnostics.DebuggerNonUserCode]
        public bool TryWrite(int timeout)
        {
            try
            {
                _lock.AcquireWriterLock(timeout);
                return true;
            }
            catch (ApplicationException)
            { return false; }
        }

        /// <summary>
        /// Releases a writer lock
        /// </summary>
        public void ReleaseWrite()
        {
            _lock.ReleaseWriterLock();
        }

        /// <summary>
        /// Returns a reader lock that can be elevated to a write lock
        /// </summary>
        public ReadLock Read() { return ReadLock.Acquire(this, -1); }

        /// <summary>
        /// Returns a reader lock that can be elevated to a write lock
        /// </summary>
        /// <exception cref="System.TimeoutException"/>
        public ReadLock Read(int timeout) { return ReadLock.Acquire(this, timeout); }

        /// <summary>
        /// Returns a read and write lock
        /// </summary>
        public WriteLock Write() { return WriteLock.Acquire(this, -1); }

        /// <summary>
        /// Returns a read and write lock
        /// </summary>
        /// <exception cref="System.TimeoutException"/>
        public WriteLock Write(int timeout) { return WriteLock.Acquire(this, timeout); }
    }
}
